1. Field of the Invention
The present invention relates to a box-shaped container of plastics material, particularly a storage and transport container. The container has a bottom with a flat upper side and a bottom side which is stabilized by stiffening ribs. Flat webs extending in a plane parallel to the plane of the bottom extend along the rim of the bottom. The flat webs form in the manner of a frame a center field of the bottom. The stiffening ribs in the center field intersect each other in the manner of a grid. The flat webs form support surfaces of the container and rest spaced apart from the plane of the bottom on stiffening ribs arranged transversely of the rim of the bottom. Pocket-shaped free spaces are formed between the bottom side of the container bottom, the upper sides of the flat webs and the transversely extending stiffening ribs, wherein the free spaces are completely open to the side of the rim of the bottom.
2. Description of the Related Art
A box-shaped container of the above-described type is known from German Patent 39 09 022. The flat webs which surround the rim portion in the manner of a frame form a bottom surface which can travel on roller conveyors, such that the box-shaped container is in the rim portion thereof provided with a second bottom, wherein the flat webs which form the lower bottom are connected through stiffening ribs to the bottom side of the actual bottom of the container in such a way that pockets are formed which are open toward the sides. The transition to the center field of the bottom is closed off over the circumference by vertical web walls at the inwardly directed rims of the flat webs. The transverse ribs and longitudinal ribs supporting the flat webs as well as the longitudinally and transversely extending stiffening ribs of the grid of ribs of the center field of the bottom are connected to the circumferentially extending vertical web. In other words, the center field of the bottom and the flat webs form an interconnected unit.
In a box-shaped container known from German Patent 41 05 527, which is improved over the box-shaped container described above, the longitudinally and transversely extending stiffening ribs of the grid of ribs of the center field of the bottom are spaced apart from the inwardly directed rims of the flat webs, so that tunnel-like free spaces are obtained between the bottom side of the container bottom, the upper sides of the flat webs and the transversely extending stiffening ribs. In contrast to the pockets of German Patent 39 09 022, which are closed at the transition to the center field of the bottom, the openings or passages at opposite ends of the tunnel-like free spaces of the container of German Patent 41 05 527 permit an almost completely unobstructed flow of cleaning liquids through the free spaces, so that, particularly when the cleaning liquids are introduced as liquid jets, the cleaning liquids can wash out all undesired residues from the free spaces. In the box-shaped container according to German Patent 41 05 527, the transverse ribs or longitudinal ribs, which support the flat webs and project inwardly beyond the flat webs, extend to the center field of the bottom and are connected to the transversely and longitudinally extending stiffening ribs of the center field.
It has been found that when high loads are placed in these known containers, even though the stiffening ribs are provided, not only the center field of the bottom, but also the bottom surface, i.e., the flat webs at the rim areas, are being bent. This may negatively influence the travel properties of the container on a roller conveyor.